Thermoplastic organic overprint inks are known in the art. The ability of such inks to accept an overprint of two or more contrasting colored inks prior to curing gives manufacturing advantages in that only a single curing step is needed to cure the multiple colors. Glass and ceramic articles, for example glass bottles, are typically decorated by screen printing. The decorating inks must be fluid and readily transferred through the screen mesh, yet set up quickly enough so second or third prints can be applied without distorting or smearing the earlier layers.
U.S. Pat. No. 5,202,162 to Hart Jr. et al. discloses a blend of thermoplastic materials that permit overprinting, but such compositions are not suited to articles that may be subjected to elevated temperatures after decorating, since the composition retains its thermoplastic nature and softens and/or becomes liquid when reheated.
Thermoset systems have been used to produce an irreversible change of state and produce cured materials which remain hard and resistant even at elevated temperatures. U.S. Pat. No. 5,346,933 to Knell discloses a blend of crystalline epoxy resin, crystalline curing agent, and either crystalline or liquid diluents to produce a composition that is screen printable at elevated temperatures, then is thermally cured to its final properties at higher temperatures. U.S. Pat. No. 5,549,929 to Scheibelhoffer discloses the use of crystalline resins and a crosslinker in conjunction with a crystalline diluent to produce compositions that are screen printable at elevated temperature and curable at higher temperatures. Both U.S. Pat. Nos. 5,346,933 and 5,549,929 stress the importance of using a diluent to reduce the viscosity of the ink for screen printing at elevated temperature, prior to the final cure. In addition, Scheibelhoffer discusses the need to use a diluent in order to yield a coating that does not have excessively high viscosity at application. The present invention obtains printable compositions without the need of a diluent.